Time interval indicating device



Aug. 21, 1934. J. A. SLEE 1,970,982

TIME INTERVAL INDICATING DEVICE Filed June 16, 1930 2 Sheets-Sheet 1 Aug. 21, 1934. J, A, LEE 1,970,982

TIME INTERVAL INDICATING- DEVICE Filed June 16, 1930 2 SheetsSheet 2 Patented Aug. 21, 1934 UNITED STATES PATENT OFFICE TIME INTERVAL INDICATING DEVICE John Ambrose Slee, Lon

don, England, assignor to Marconi International Marine Communication Company, Limited, London, England Claims.

This invention relates to time interval indicating devices, and more particularly to direct reading millichronographs for accurately indieating the time interval between two electrical impulses.

According to this invention, a millichronometer comprises a flywheel of relatively large mass; means for driving said flywheel at a relatively high constant speed, i. e., a speed such that the time required for a complete revolution ordinarily will be somewhat greater than the time interval to be measured; a driven member associated with an armature and pointer or the like; means for putting said driven member into magnetic driving connection with said flywheel upon receipt of a first impulse (which then ceases) a relatively weak magnetic hold-on system for maintaining said driving connection when once established; and a stationary magnet energized upon receipt of a second impulse which then ceases for capturing the driven member from the driving flywheel and stopping said member in the position it has reached in the time between the impulses. Preferably means are provided for visibly indicating whether or not the driving member is rotating at the correct speed.

Preferably also means are provided for reducing the duration of each impulse to a predetermined period and for assuring definite rates of growth of current through the various wind ings of the instrument, so that the time lags of each of the various operations shall be constant.

In one form of construction, an instrument in accordance with this invention comprises a fly wheel of relatively large mass which is driven at a constant speed of relatively high value having regard to the timeTnterval to be measured. A driven member associated with an armature and pointer is provided andthe said flywheel and driven member are arranged to be put in magnetic driving connection upon reception of the first impulse and maintained in driving connection by means of a relatively weak hold-on magnetic system, until the second impulse arrives. Upon reception of the second impulse, a stationary magnet provided captures the driven member from the driving flywheel and holds it stationary in whatever position it shall have reached during the time interval between the two impulses. The

which indicates the time interval. A switch is provided for breaking the circuit of the stationary magnet when a reading has been taken, whereupon a small hair or other recovery spring connected to the pointer returns it to its initial pointer .moves. over .a scale, the reading uponposition. If it be desired, as for instance, when the duration of the first impulse is not very short as compared to the interval between the impulses, means may be provided for limiting the period during which the actual impulses affeet the instrument, so that the said instrument measures the time interval between the-beginnings of the impulses.

Where the impulses are likely to be of widely different intensities, it is preferred that they actuate the instrument through a mechanical or thermionic relay or similar device.

The invention is illustrated in the accompanying schematic and diagrammatic drawings, Figures 1 and 2 showing the mechanical arrangements, and Figure 3 the circuit connections of one construction of instrument in accordance with the invention; Figure 4 shows a detail modification which can be substituted for part of the apparatus in the instrument illustrated in Figures 1 to 3.

Referring to Figures 1 and 2, A is a flywheel which is driven at substantially constant speed by a suitable motor, B, the bearings of said flywheel being such as to leave only a free small end play of the order of .001 inch. Carried on the flywheel is a pin N which may be adjustable in position and is located near the periphery. O is a window fitted at one end OR. with a red glass and at the other 0G with green glass, there being a small space 03 between the glasses. Adjacent the flywheel and overlapping it is a time check device consisting of an oscillating disc J mounted in free bearings and held by a light spring K against a stop L. The disc J carries a pallet M, one end of which engages the stop L and the whole assembly consisting of the parts J K M should be statically balanced if the apparatus is to be exposed to vibrations or to movements likely to affect the time period of the device by reason of inertia effects or otherwise. If desired, compound arms and balance weights may be provided on the disc J so as to maintain its period constant under varying temperatures. Cut in the disc J near the periphery thereof is a sighting hole R and the -whole arrangementis such that when the flywheel A and disc J are in certain positions, light from a source P, associated with a suitable optical projection device, will shine through the window 0 and thesighting hole R. v As the flywheel.

rotates, the, pin N will, each revolution, engage the pallet M and carry the disc J through a part of av revolution, the pin N disengaging fromjthe pallet M at some predetermined point, and permitting the return of the disc J so that the hole R will reach a predetermined position at some known and constant time interval after disengagement. The parts are so adjusted that when the flywheel A is revolving at correct speed, the source of light will shine, once per revolution, through the part 03 of the window 0, thus giving a white flash. If the flywheel A revolves too fast, the light will shine through, say, the green portion 0G, and if it revolves too slowly, a red flash will show. In this way visible indication of correct speed of the flywheel is given.

Carried on the flywheel A is a magnet C of the pot type, for example, having two windings, an operating winding CWO (Figure 3) and a holding winding CWH, the latter being shunted by an adjustable resistance WR, the two windings being connected through slip rings to stationary terminals. Facing the magnet C and close to it is a stationary magnet D, preferably of a type different from that of the magnet C. The magnet D has two windings, an operating winding DWO and a holding winding DWH (Figure 3) The first winding may, if desired, be dispensed with and a single winding utilized for both purposes. The armature E is mounted in bearings giving it free movement both axially and rotarily and carries a pointer F which co-operates with a scale G and is normally held against a stop corresponding to the zero reading by means of a light spiral spring H.

The impulses whose time interval is to be measured are supplied through terminals Q connected to diagonally opposite points of a resistance-inductance bridge LR across whose other diagonally opposite points are connected the windings a of a relay 1). Thus the relay 1) will be operated during growth of a current impulse at the terminals Q, but will return to its inoperative position when the current impulse reaches a steady value. It will be seen that the bridge and relay combination transforms applied impulses into output impulses (from the relay) of substantially uniform predetermined rates of growths and values and limited duration.

The tongue (1 of the relay b is insulated, and connected to the grid of a suitable three-electrode valve 6. When the relay 1) is in a position of rest, its tongue at bears against the spacing stop I of the relay, and is thus connected to a suitable negative bias (say, 20 volts) for the grid of the valve e. The anode current of the valve e will in this case be zero, or any other desired small value. When the relay b operates, the tongue d touches the .marking stop g which is connected to some other suitable bias (say, 20 volts positive) for the grid of the valve e. The anode current of the valve e will then rise abruptly to some definite value (say, 50 milliamperes). The anode current of the valve e will continue to flow until the tongue d of the relay 11 returns to the spacing stop 1. Alternatively, the relay tongue d can be arranged to operate the milli-chronograph directly.

If desired the above described relay and associated circuit may be replaced by a thermionic valve circuit adapted to transform applied impulses into output impulses of substantially uniform predetermined rates of growths and values and limited duration. A suitable circuit of this kind is shown diagrammatically in Fig. 4 in which a thermionic valve 1 having in its grid circuit the secondary of a transformer 2 and a source of bias potential (e. g. a battery 3) is employed. The primary of the transformer 2 is subjected to applied impulses through a condenser 4 the said condenser and primary being shunted as shown by a leak resistance 5. The various components are so chosen and adjusted that the anode circuit of the valve 1 only carries current so long as the current in the primary of transformer 2 is growing, 1. e. so long as the condenser 4 is taking a charge. The resistance 5 serves to leak away the charge in condenser 4 in time to allow the apparatus to be ready to receive the second impulse and this time can of course be varied by adjusting the said resistance 5. Obviously the condenser and resistance must be so chosen as to operate satisfactorily with the apparatus which is supplying input impulses; e. g. regard must be paid to the characteristics of, say, the final valve in an amplifier whose output terminals are to supply input impulses for the present apparatus. It will be understood that the arrangement shown in Figure 4 may be substituted for the resistance-inductance bridge LR and the valve e of Figure 3 by connecting the elements of the valve 1 to the relay circuit shown in the lower part of Figure 3 in the same manner that corresponding elements of the valve e are shown connected to such circuit.

In the rest or idle position of the instrument, the contacts h and 7' are normally closed and the anode current of the valve e passes through the tongue h of a change-over relay 8 to the contact a of said relay, and thence to the operating winding CWO of the revolving magnet C and the operating winding T0 of a hold-on relay T, thus causing the armature E to be seized and carried round by the revolving magnet C, an? closing the contacts 1 of the hold-on magne T.

On being closed, the contacts 1 apply a suitable source of electric supply to a circuit containing the hold-on coils TH of the hold-on relay T and a resistor X, the operating coil of the changeover relay S, and the hold-on winding CWH of the revolving magnet C. The armature E is thus caused to adhere to the face of the revolving magnet C after the original impulse has ceased, and the tongue h 01' the change-over relay 8 is pulled over to the contact w and held there.

The apparatus is now ready to receive the second impulse which is applied by the relay b as before. In this case the operating current passes through the tongue 71. of the change-over relay S, and through its contact 10, thus passing through a circuit containing the operating winding DWO of the stationary magnet D and the operating winding UO of a second hold-on relay U, thus causing the armature E to be captured from the revolving magnet C and held stationary. I! desired the winding DWO may be dispensed with, the winding in circuit with the contacts of the hold-on relay U being employed for both duties.

The contacts I of this relay U control a circuit containing the hold-on coil UH of the relay U, a resistor Y, and the hold-on coil DWa of the stationary magnet D. The armature E and the pointer F are thus held stationary after the second impulse has ceased, and continue to be held until current is switched off from the apparatus, when the pointer F will return to its zero position under the influence of the spring H.

In order to counteract the tendency of the armature E to adhere to the stationary magnet D, a switch V is arranged so that in the act of switching of! the current, a momentary demagnetizing current is applied through a resistor Z to the hold-on windings DWa of the stationary magnet D, and to the hold-on coil UH of the re y U. V

The variable resistance WR is adjusted so as to regulate the grip of the hold-on winding of the revolving magnet.

It will be seen that with this arrangement, if the first impulse persists for too long a period, the tongue h of the relay S will reach the contact to before the first impulse ceases, and if this happens, the second part of the action will take place and the pointer F will be stopped and held.

In order to prevent injury to the pointer F, should the interval between the impulses to be measured prove to be longer than the time occupied by one complete'revolution of the revolving magnet, a safety contact I is arranged so as to be operated by the pointer F just before it completed a revolution. This contact is connected in circuit with the stationary magnet D through a resistor 50 and operates the magnet D to capture the armature E and hold it and the pointer F locked before any injury can be done to the pointer F by striking the back of the zero stop.

The apparatus will be the more consistent in its readings as the rate of growth of current in its circuits can be increased, and as the inertia of the moving parts can be reduced. If a large number of exactly equal periods are measured, the pointer should indicate exactly equal readings if the instrument is perfectly consistent. Greater consistency may be obtained by energizing the magnet windings from a source of comparatively high voltage, the current being kept down to the requisite maximum by the insertion of suitable non-inductive resistances.

Small alterations in the time intervals to be measured can only be detected if the instrument is consistent and instruments can be constructed according to the methods described which will detect alterations in time periods of about 1/1000 of a second.

The accuracy of the measurements depends on the constancy of the angular velocity of the flywheel throughouteach revolution, and on the constancy of the time-lag of the revolving and stationary magnets. These two time-lags should be equal, otherwise an error corresponding to index error will be produced. As there are limits to the velocity at which theflywheel can be run without inconvenience, it may be advisable to insert gears between the shaft of the armature E and the pointer F in order to obtain a suitable scale for reading abnormally short or abnormally long periods, but such an addition will not affect the consistency or the accuray of the instrument, if backlash in the gearing is avoided. Gearing the pointer will only allow of the use of a more convenient scale.

One application of this invention is the measurement of the depth of water under a ship, or for similar purposes.

In such a case the first impulse is given by the transmission through water of a sound wave,

-either periodic or of a predetermined frequency,

and the second impulse is given by the arrival at the ships hull of the reflection of this sound wave from the bottom of the sea.

In such a case it is convenient to adjust the speed of the flywheel so that one degree of angular advance corresponds to a depth of one fathom below the source of the sound wave. It is usual in such cases to place the projector and receiver in the bottom of the ship. Where it is practicable to fit the projector and receiver very close together, or to make use of the same piece of apparatus for both purposes the instrument may be made to indicate directly the depth of water from the surface by moving the starting position of the pointer to position on the scale indicating the depthor average depth -of the projector and receiver below the surface. This adjustment can readily be varied in accordance with the draught of the ship.

What I claim is:

1. A mini-chronograph comprising in combination a driving member, means for rotating said member at a substantially constant speed, a driven member, an indicator actuated thereby, means operable upon the reception of a first electrical impulse for establishing driving connection between said driven member and said driving member, a stationary member operable upon reception of a second impulse effectively to break the said driving connection and retain the driven member in whatever position it shall have reached during the interval in which it was driven, and means for rendering the instrument substantially independent of non-uniformity in the impulses, said last mentioned means comprising a reactance-resistance bridge, a relay connected across one diagonal thereof and means for applying the impulses across the other diagonal whereby the relay is actuated only during the growing current period of an impulse so that input impulses are transformed into output impulses of substantially uniform predetermined rates of growth and values and limited duration.

2. A milli-chronograph comprising in combination a driving member, means for rotating said member at a substantially constant speed, a driven member, an indicator actuated thereby, a magnetic winding operable upon the reception of a first electrical impulse for establishing driving connection between said driven member and said driving member, a stationary magnetic winding operable upon reception of a second impulse effectively to break the said driving connection and retain the driven member in whatever position it shall have reached during the interval in which it was driven, and impulse receiving means comprising a thermionic valve having input and output circuit connections between said input circuit and said windings to which impulses are applied, and means for controlling through said valve the impression of impulses on said driven member.

3. In a millichronometer, a flywheel of relatively large mass, driving means for'driving said flywheel at a desired predetermined substantially constant speed, a driven member, an armature and indicating means associated with said driven member, magnetic coupling means between said driven member and said flywheel, an energizing circuit for said magnetic coupling means, means operable upon receipt of a first impulse which then ceases for completing said energizing circuit, a relatively weak magnetic hold-on system for maintaining said magnetic coupling when once established, a stationary magnet, a circuit for energizing said stationary magnet, means operable upon receipt of a second impulse which then ceases for completing said last mentioned energizing circuit whereby the driven member is captured from the driving flywheel and thus stopped in whatever position it shall have reached during the time interval between the impulses and means for rendering the instrument independent of nonuniformity in the impulses, said last mentioned means including a resistance reactance bridge, a relay having a winding connected across one diagonal thereof and means for applying the impulses across the other diagonal whereby the relay is actuated only during the growing current period of an impulse so that input impulses are transformed into output impulses of substantially uniform predetermined rates of growth and values and limited duration.

4. In a millichronometer, a flywheel of relatively large mass, driving means for driving said flywheel at a desired predetermined substantially constant speed, a driven member, an armature and indicating means associated with said driven member, magnetic coupling means between said driven member and said flywheel, an energizing circuit for said magnetic coupling means, relay means for receiving operating impulses, means operable upon receipt of a first impulse which then ceases for completing said energizing circuit, a relatively weak magnetic hold-on system for maintaining said magnetic coupling when once established, a stationary magnet, a circuit for energizing said stationary magnet, means operable upon receipt of a second impulse which then ceases for completing said last mentioned energizing circult whereby the driven member is captured from the driving flywheel and thus stopped in whatever position it shall have reached during the time interval between the impulses and means for rendering the instrument independent of non-uni i'ormity in the impulses, said last mentioned means including a resistance reactance bridge, a

. relay having a winding connected across one diagonal thereof and means for applying the impulses across the other diagonal whereby the relay is actuated only during the growing current period of an impulse so that input impulses are transformed into output impulses of substantially uniform predetermined rates of growth and values and limited duration.

5. In a millichronorneter, a flywheel of relatively large mass, driving means for driving said flywheel at a desired predetermined relatively high substantially constant speed, a driven member, an armature and indicating means associated with said driven member, magnetic coupling means between said driven member and said flywheel, an energizing circuit for said magnetic coupling means, relay means for receiving operating impulses, means operable upon receipt of a first impulse which then ceases for completing said energizing circuit, a relatively weak magnetic holdon system for maintaining said magnetic coupling when once established, a stationary magnet, a circuit for energizing said stationary magnet, means operable upon receipt of a second impulse which then ceases for completing said last mentioned energizing circuit whereby the driven member is captured from the driving flywheel and thus stopped in whatever position it shall have reached during the time interval between the impulses and a thermionic valve for controlling the impression of said impulses on said flywheel.

JOHN AIVIBROSE SLEE. 

